PROJECT SUMMARY The ability to survive periods without food is the cornerstone of evolution and life on earth. Mammals respond to fasting by activating mechanisms that stimulate appetite, while at the same time increasing hepatic glucose production in order to keep the brain nourished and alert while exogenous calories are sought and acquired. This is accomplished through a cascade of enzymatic reactions and processes in the brain and the liver that are precisely coordinated by an array of hormones. We recently discovered a protein hormone called asprosin that regulates mammalian glucose homeostasis. Since then, we have found that asprosin also regulates appetite by activating orexigenic AgRP neurons in the arcuate nucleus of the hypothalamus. This results in downstream anorexigenic POMC neuron inhibition, in a GABA-dependent manner. This asprosin-mediated chain of events leads to appetite stimulation and a drive to accumulate adiposity and body weight. Genetic deficiency of asprosin in humans results in a syndrome characterized by low appetite and extreme leanness, phenocopied by mice carrying similar mutations, and fully rescued by correcting the asprosin deficiency. Obese humans and mice display pathologically elevated circulating asprosin levels, and neutralization of plasma asprosin using monoclonal antibodies reduces appetite and body weight in such mice, in addition to improving their glycemic profile. Thus, asprosin, in addition to performing a glucogenic function, is an orexigenic hormone, and anti-asprosin antibodies show therapeutic potential as dual-action anti-obesity/anti-diabetes agents. This proposal seeks to build on these observations with a broad aim of enhancing our understanding of asprosin's orexigenic effect and the anti-obesity potential of asprosin-neutralization therapy. We seek to do so within the following 3 aims: 1) Determine the contribution of adipose-derived asprosin on AgRP neuron activation. 2) Determine the necessity and sufficiency of the SK3- mediated outward potassium current on asprosin-mediated AgRP neuron activation and appetite stimulation. 3) Map the anti-obesity potential of anti-asprosin monoclonal antibodies. At the completion of these aims we expect to determine the relevance of asprosin on central regulation of appetite and adiposity, and how this process can be manipulated to therapeutically impact obesity.